The present invention relates in general to vehicles such as tractors and the like, and in particular to a tractor for agriculture having at least one engine-driven wheel axle for propelling the tractor, which is selectively connected to the engine by either a hydraulic stepless speed change mechanism or an alternate transmission mechanism employed when trouble occurs in the operation of the hydraulic stepless speed change mechanism.
A prior known tractor includes the power transmission system shown in FIG. 8. Namely, a transmission change mechanism (0C) is disposed between an intermediate portion of an input shaft assembly (011) from an engine (01) to a hydraulic stepless speed change mechanism (02) and an intermediate portion of a transmission shaft assembly (0Y) from the hydraulic stepless speed change mechanism (02) to an output shaft (012), to by-pass the hydraulic stepless speed change mechanism (02), said transmission change mechanism (0C) being connectable and disconnectable of power transmission from the output shaft (012) to a running device (0X) and capable of power transmission from the intermediate portion of the input shaft assembly (011) to the running device (0X). According to this construction, when the hydraulic stepless speed change mechanism (02) is in trouble, it is possible to take emergency measures for continuing running of the tractor by transmitting a power from the intermediate portion of the input shaft assembly (011) to the running device (0X) by operating the transmission change mechanism (0C).
However, this known tractor includes a large and complex transmission case for housing the transmission change mechanism (0C) which greatly increases the cost of the tractor, even though this known emergency running mechanism is only used infrequently, when the hydraulic stepless speed change mechanism is in trouble.